When using Visual Studio (2005)and clicking on Help I can choose the Intel C++ documentation. I can see differences and extensions over what MS C++ has but I cannot look in the index to locate items in the C++ language and runtime support. For this I have to open MS C++ and obtain the information from there. Hence "Why no C++ documentation with C++ documantation".
For example, I wanted to see if the Intel C++ had enhancements to the intrinsic function to read the CPUID. _cpuid is not listed nor is virtually everything else related to compiler intrinsics and C++ language altogether.